Tao Zhang 1*, Kuiying Yu 1 and Xuhua Li 2

Transcription

1 Zhang et al. BMC Cardiovascular Disorders (2018) 18:29 RESEARCH ARTICLE Open Access Cytochrome P450 family 4 subfamily F member 2 (CYP4F2) rs , rs polymorphisms and susceptibility to several cardiovascular and cerebrovascular diseases Tao Zhang 1*, Kuiying Yu 1 and Xuhua Li 2 Abstract Background: Inconsistent conclusions have been reported for the genetic relationship between CYP4F2 (Cytochrome P450 Family 4 Subfamily F Member 2) polymorphisms and the susceptibility to cardiovascular and cerebrovascular diseases. Methods: We performed a meta-analysis to assess the potential role of rs C/T and rs G/A polymorphisms of CYP4F2 in the risks of cardiovascular and cerebrovascular diseases. The retrieval of four databases, including PubMed, Web of Science (WOS), China National Knowledge Infrastructure (CNKI) and WANFANG DATA, was conducted. Mantel-Haenszel statistics for association test, Cochran s Q statistic, sensitivity analysis for heterogeneity assessment, and Begg s/egger s tests for publication bias evaluation were performed under allele, homozygote, heterozygote, dominant, and recessive models, respectively. Results: A total of 597 articles were initially obtained by database searching, and twenty eligible articles were finally included. For rs , a decreased risk of cardiovascular and cerebrovascular diseases was observed in the overall meta-analysis and in hypertension, population-based and male subgroups under models of T vs. C, CT vs. CC, and CT + TT vs. CC [all P values in association tests < 0.05, odds ratio (OR) < 1]. For rs , a decreased coronary artery disease (CAD) risk was observed in the subgroup meta-analysis based on disease type under all genetic models (all P values in association tests < 0.05, OR< 1). Begg s/egger s tests excluded the potential publication bias, while sensitivity analysis data supported the stability of the above results. Conclusion: C/T genotype of CYP4AF2 rs may be linked to the decreased risk of hypertension in the male patients of Asian populations, while CYP4F2 rs is likely associated with reduced susceptibility to CAD. Keywords: CYP4F2, Single nucleotide polymorphisms, Coronary artery disease, Hypertension, Ischemic stroke Background Single nucleotide change-induced nucleic acid sequence polymorphisms, namely, single nucleotidepolymorphisms (SNPs), occur more frequently in the human genome, with an average of approximately one polymorphism per 1000 bases, and functional SNPs may help to guide population genetics research, as well as the mechanistic, epidemiologic * Correspondence: zbsjnk@163.com 1 First Department of Neurology, The First Hospital of Zibo, No.4 Emei Mountain Road, Boshan District, Zibo City, Shandong , People s Republic of China Full list of author information is available at the end of the article or diagnostic study of some clinical genetic diseases [1, 2]. Emerging SNPs of different genes have been implicated in the complicated etiology or pathogenesis of several cardiovascular and cerebrovascular diseases [3 5]. For example, GWAS (genome-wide association studies) data show that some SNPs, such as rs of the CYP17A1 (Cytochrome P450 Family 17 Subfamily A Member 1) gene or rs of the ATP2B1 (ATPasePlasmaMembrane Ca 2+ Transporting 1) gene, are associated with susceptibility to blood pressure or essential hypertension [6, 7]. The aim of the present study was to investigate the potential role of the CYP4F2 (Cytochrome P450 Family 4 Subfamily The Author(s) Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

2 Zhang et al. BMC Cardiovascular Disorders (2018) 18:29 Page 2 of 10 F Member 2) polymorphism in the risk of cardiovascular and cerebrovascular diseases, such as myocardial infarction (MI), coronary artery disease (CAD), ischemic stroke (IS), cerebral infarction (CI) and hypertension. Human CYP4F2 gene is located on chromosome 19 and contains 12 introns and 13 exons [8]. There are several common SNPs, such as rs , rs , rs , rs and rs [8, 9]. The SNPs of rs , rs , rs , and rs are located in the intron region of the CYP4F2 gene, while rs (namely, V433 M, G1347A, and G20597A) is located in the exon region of this gene [8, 9]. CYP4F2 protein belongs to the human cytochrome P450 superfamily and functions as an essential enzyme for the production of 20-HETE (20- hydroxy eicosane arachidonic acid) [10, 11]. Increased 20-HETE levels are associated with vascular oxidative stress, endothelial dysfunction and high peripheral vascular resistance [10, 12]. As a bioactive eicosanoid and therapeutic intervention target, 20-HETE is involved in several vascular events, such as the modulation of blood pressure, renal function, cerebral blood flow and pulmonary circulation [10, 12]. Considering the conflicting conclusions, we quantitatively measured the genetic correlation between CYP4F2 SNPs and the risk of cardiovascular and cerebrovascular diseases via meta-analysis based on the publicly published data. To our knowledge, one meta-analysis of hypertension [13] and another meta-analysis of ischemic stroke [14] were previously reported for CYP4F2 rs However, no metaanalysis for the other SNPs of the CYP4F2 gene have been reported. Additionally, there is no meta-analysis regarding theroleofcyp4f2 rs in the risk other cardiovascular and cerebrovascular diseases. Methods Database searching In accordance with the methodology of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [15], we performed the retrieval of four electronic databases, including PubMed, Web of Science (WOS), China National Knowledge Infrastructure (CNKI) and WANFANG DATA, up to Jan Considering the limitation of publication space, the searching terms for each database are listed in supplemental online Additional file 1: TableS1. Selection criteria After screening, eligible case-control studies provided the sufficient genotype frequency data of CYP4F2 gene in each case/control group. The following exclusion criteria were considered: a) animal or cell experiments; b) other genes/diseases or non-snp gene variants; c) meeting abstract; d) meta-analysis; e) review or letter; f) undetected variants; g) the absence of genotype frequency data; h) duplicated articles; and i) not in HWE (Hardy-Weinberg- Equilibrium). Basic information We extracted the basic information from the eligible articles, namely, first author, year, ethnicity, genotyping assay, SNPs, genotype frequency, disease type, gender, mean age, study number, sample size of the case/control, X 2 and P values of HWE, and source of control. The paper quality was assessed by the Newcastle-Ottawa Scale (NOS) system [16], which indicates poor quality when the NOS score is less than five. Statistical analysis Based on Mantel-Haenszel statistics, the value of OR (odds ratio), 95% CIs (confidence intervals) and P value of association test was generated under the allele, homozygote, heterozygote, dominant, and recessive models. A fixed-effect model was used when the P value of heterogeneity from Cochran s Q statistic was larger than 0.05 or I 2 less than 50.0%. Subgroup meta-analyses by ethnicity (Caucasian/Asian), disease type (hypertension/cad/is/ CI/MI), source of control (population/hospital -based), and gender (male/female), were also conducted through Mantel-Haenszel statistics. For publication bias assessment, Begg s/egger s tests were performed. Stata/SE software version 12.0 (StataCorp LP,College Station, TX USA) was used for the above statistical analyses. Results Eligible case-control studies Eligible case-control studies were obtained following the flow diagram of Fig. 1. We first obtained 597 articles from database searching, namely, PubMed with 128 articles, WOS with 369 articles, CNKI with 36 articles, and WANFANG DATA with 65 articles. Next, we removed 105 articles with duplicated data and 432 articles did not met the inclusion criteria. A total of 60 full-text articles were then assessed for eligibility. We further removed 40 articles for undetected variants or the absence of genotype frequency data. Finally, 20 articles [8, 9, 17 34] were included in the present meta-analysis. The basic information and genotype frequencies of eligible casecontrol studies for the present meta-analysis are provided in Additional file 1: Tables S2-S5. Two polymorphisms within the CYP4F2 gene (rs C/T and rs G/A) were analyzed. The NOS system data suggested that no included studies showed poor quality, as all NOS scores were larger than five (Additional file 1: Table S3). Moreover, all the genotype distributions of controls adhered to Hardy-Weinberg Equilibrium (Additional file 1: Table S4-S5).

3 Zhang et al. BMC Cardiovascular Disorders (2018) 18:29 Page 3 of 10 Fig. 1 Flow diagram of the eligible case-control studies identified The rs C/T polymorphism We first conducted a meta-analysis to analyze the association between CYP4AF2 rs C/T and risk of cardiovascular and cerebrovascular diseases. In Table 1, ten case-control studieswith3462casesand3547controlsinanasianpopulation were enrolled [8, 18, 19, 21, 22, 25, 27, 33, 34]. Overall meta-analyses and subgroup analyses were conducted under allele (G vs. A), homozygote (GG vs. AA), heterozygote (AG vs. AA), dominant (AG + GG vs. AA), and recessive (GG vs. AA+AG) genetic models. There was no high degree of heterogeneity in any of the meta-analyses (Table 1, I 2 value =0.0%, P value of heterogeneity > 0.05), and fixedeffect model was applied. In pooled data from overall meta-analysis (Table 1), a decreased risk of cardiovascular and cerebrovascular diseases was observed between case and control groups (T vs. C, P value in association tests = 0.021, OR = 0.92; CT vs. CC, P = 0.024, OR = 0.89; CT + TT vs. CC, P = 0.012, OR = 0.88). Moreover, similar results were observed under allele, heterozygote and dominant genetic models in hypertension and population-based subgroups (Table 1, all P value in association tests < 0.05, OR< 1). We also performed a subgroup analysis based on gender. As shown in Additional file 1: Table S6, a reduced hypertension risk was observed in the male subgroup under allele (P value in association tests < 0.001, OR = 0.79), homozygote (P = 0.009, OR = 0.68), heterozygote (P < 0.001, OR = 0.67) and dominant (P < 0.001, OR = 0.67) genetic models. Figure 2 shows the forest plot of thesubgroupanalysisbydiseasetypeundertheheterozygote model, and Additional file 2: FigureS1and Additional file 3: Figure S2 presents the data under allele and dominant models. Additional file 4: FigureS3 shows the forest plot of subgroup analysis by gender under the allele model. Thus, these results demonstrated that the C/T genotype of CYP4AF2 rs might be associated with a reduced risk of hypertension in the male patients of Asian populations. The rs G/a polymorphism Meta-analysis of the association between the CYP4AF2 rs G/A polymorphism and the risk of cardiovascular and cerebrovascular diseases was subsequently performed. A total of 17 case-control studies were enrolled [8, 9, 17 20, 23, 24, 26 32, 34]. As shown in Table 2, a random-effects model was used in all meta-analysis (all P value of heterogeneity < 0.05). A decreased CAD risk was observed in the subgroup meta-analysis by disease type under all genetic models (Table 2, Avs.G,P value in association tests =0.001, OR = 0.78; AA vs. GG, P =0.001, OR = 0.55; GA vs. GG, P = 0.002, OR = 0.80; GA + AA vs.

4 Zhang et al. BMC Cardiovascular Disorders (2018) 18:29 Page 4 of 10 Table 1 Meta-analysis of CYP4AF2 rs C/T polymorphism Genetic models Subgroup Test of association N Sample size Heterogeneity OR (95% CIs) z P value case control I 2 P value allele (T vs. C) overall/asian 0.92 (0.86, 0.99) % hypertension 0.89 (0.81, 0.98) % CAD 1.00 (0.87, 1.14) % population-based 0.91 (0.85, 0.98) % homozygote (TT vs. CC) overall 0.87 (0.76, 1.00) % hypertension 0.85 (0.70, 1.04) % CAD 0.99 (0.76, 1.30) % population-based 0.85 (0.70, 1.04) % heterozygote (CT vs. CC) overall/asian 0.89 (0.80, 0.98) % hypertension 0.81 (0.70, 0.93) % CAD 0.98 (0.79, 1.21) % population-based 0.87 (0.78, 0.97) % dominant (CT + TT vs. CC) overall 0.88 (0.80, 0.97) % hypertension 0.82 (0.71, 0.93) % CAD 0.98 (0.80, 1.20) % population-based 0.86 (0.78, 0.96) % recessive (TT vs. CC + CT) overall/asian 0.93 (0.82, 1.06) % hypertension 0.95 (0.80, 1.14) % CAD 1.01 (0.80, 1.28) % population-based 0.92 (0.80, 1.06) % OR odds ratio, CIs confidence intervals, CAD coronary artery disease, N number of case-control studies GG, P = 0.005, OR = 0.77; AA vs. GG + GA, P = 0.002, OR = 0.60). However, no significant associations were observed for other factors (Table 2 and Additional file 1: Table S7). Figure 3 shows the forest plot of the subgroup analysis by disease type under the allele model, and Additional file 5: Figure S4, Additional file 6: Figure S5, Additional file 7: Figure S6 and Additional file 8: FigureS7 presents the data of homozygote, heterozygote, dominant and recessive models. Additional file 9: Figure S8 shows the forest plot of subgroup analysis by gender under the allele model. These data indicated that the CYP4AF2 rs G/A polymorphism was associated with reduced susceptibility to CAD. Publication bias/sensitivity analysis Table 3 shows the results of Begg s/egger s tests under all genetic models (P value in Begg s test > 0.05; P value in Egger s test > 0.05), suggesting the absence of large publication bias. Fig. 4a presents the funnel plot of Egger's test under the allele model of the CYP4AF2 rs G/A polymorphism. Furthermore, we observed the stability of the above data based on the sensitivity analysis (Fig. 4b for allele models of rs , other models not shown). Discussion CYP4AF2 rs SNP was reportedly associated with an increased risk of hypertension cases in India [26] or Northern Han Chinese patients [23]. However, negative data were observed in another study in China [32]. In 2015, Luo et al. performed a meta-analysis of four studies [8, 19, 23, 32] andfoundthatthecyp4af2 gene rs polymorphism was not associated with hypertension risk [13]. Here, eight case-control studies [8, 19, 20, 23, 26, 27, 29, 32] wereincludedinourmetaanalysis, and negative correlation between CYP4AF2 rs and hypertension risk was observed. Nevertheless, we first investigated the role of CYP4AF2 rs in the risk of hypertension. The findings suggested that the C/T genotype of CYP4AF2 rs was correlated with a reduced risk of hypertension in the male patients of Asian populations. As a metabolite of arachidonic acid (AA), partly by CYP4F2 protein, 20-HETE induces the transcription of ACE (angiotensin-converting enzyme) gene through stimulating the NF-ΚB pathway and contributes to the pathophysiology of hypertension [10]. CYP4AF2 rs , located in an intron region, likely affects the enzyme activity of CYP4F2 protein during 20- HETE metabolism through altering the gene transcription

5 Zhang et al. BMC Cardiovascular Disorders (2018) 18:29 Page 5 of 10 Fig. 2 Subgroup analysis by disease type of the association between the CYP4AF2 rs polymorphism and the risk of cardiovascular and cerebrovascular diseases under the heterozygote model level, RNA secondary structure or RNA splicing of the CYP4AF2 gene, which is worth further investigation of the molecular mechanism. In addition, CYP4F2 rs was tightly associated with systolic blood pressure as well as the excretion of 20-HETE [29]. Additional case-control studies are needed to further confirm the role of CYP4F2 rs in hypertension risk. Coronary heart disease results from the interplay between polygenic predisposition and complex environmental factors [35]. The CYP4AF2 gene rs polymorphism was associated with the risk of coronary artery disease in a Han Chinese population [9]. However, a negative correlation between the CYP4AF2 rs and coronary heart disease risk was reported in Mongolian cases in China [34]. In the present study, we first examined whether the CYP4AF2 rs polymorphism is likely associated with the reduced susceptibility to coronary artery disease. Here, the meta-analysis provided evidence of the involvement of CYP4AF2 rs in susceptibility to coronary heart disease. Given the reported correlation between CYP4AF2 rs and 20-HETE [36], functional CYP 4AF2 rs may mediate the nonsynonymous mutation of a valine (V) located at residue 433 to a methionine (M), namely, V433 M, which then leads to the alteration of CYP4F2 protein function and 20-HETE synthesis, thereby influencing the occurrence of coronary heart disease. The early evaluation of genetic risk factors is essential for the effective diagnosis and treatment of clinical ischemic stroke [3, 37]. We observed different conclusions for the association between CYP4AF2 SNPs and ischemic stroke risk. For example, no detectable difference was reported by Liao, et al. for the genotype distribution of CYP4AF2 rs between the control and cases of ischemic stroke [24]. However, Munshi, et al. reported CYP4AF2 rs SNP as an important risk factor for ischemic stroke in an Indian population [26]. In 2015, Meng, et al. performed a meta-analysis of ischemic stroke and rs under the GA + AA vs. GG model [14], enrolling six studies [18, 20, 21, 26, 30, 38], and reported the data of OR> 1, P < [14]. In the present study, we removed two studies that did not contain the genotype data [20, 38] and one study on cerebral infarction [21], added one new study published in 2016 [24], and finally four studies [18, 24, 26, 30] were enrolled. Additionally, the GA + AA vs. GG model, and other genetic models,

6 Zhang et al. BMC Cardiovascular Disorders (2018) 18:29 Page 6 of 10 Table 2 Meta-analysis of CYP4AF2 rs G/A polymorphism Genetic models Subgroup Test of association N Sample size Heterogeneity OR (95% CIs) z P value case control I 2 P value allele (A vs. G) overall 0.95 (0.87, 1.04) , % < Asian 0.95 (0.87, 1.04) % < CAD 0.78 (0.68, 0.90) % IS 0.93 (0.74, 1.18) % hypertension 1.07 (0.99, 1.15) % population-based 0.92 (0.81, 1.05) % < homozygote (AA vs. GG) overall 0.94 (0.76, 1.16) , % < Asian 0.90 (0.71, 1.16) % < CAD 0.55 (0.39, 0.77) % IS 0.90 (0.56, 1.44) % hypertension 0.90 (1.02, 1.37) % population-based 0.91 (0.70, 1.19) % heterozygote (GA vs. GG) overall 0.95 (0.89, 1.01) , % Asian 0.92 (0.85, 1.00) % CAD 0.80 (0.69, 0.92) % IS 0.94 (0.80, 1.09) % hypertension 1.00 (0.93, 1.09) % population-based 0.91 (0.83, 0.99) % dominant (GA + AA vs. GG) overall 0.93 (0.83, 1.03) , % Asian 0.91 (0.80, 1.03) % CAD 0.77 (0.64, 0.92) % IS 0.93 (0.71, 1.21) % hypertension 1.03 (0.95, 1.12) % population-based 0.89 (0.77, 1.03) % < recessive (AA vs. GG + GA) overall 0.98 (0.82, 1.18) , % Asian 0.95 (0.77, 1.17) % CAD 0.60 (0.44, 0.83) % IS 0.93 (0.65, 1.33) % hypertension 1.22 (1.05, 1.43) % population-based 0.96 (0.77, 1.19) % OR odds ratio, CIs confidence intervals, CAD coronary artery disease, IS ischemic stroke, N number of case-control studies including A vs. G; AA vs. GG; GA vs. GG; AA vs. GG + GA, were utilized. We obtained a negative result for the genetic relationship between ischemic stroke risk and the CYP4AF2 gene rs polymorphism. Different searches and analysis strategies might contribute to this finding. We found that not all control data in these studies were population-based. After removing studies with hospitalbased control data, the same positive correlation between the CYP4AF2 rs C/T polymorphism and risk of cardiovascular and cerebrovascular diseases was obtained under allele, heterozygote and dominant genetic models. In addition, sensitivity analysis indicated the stability of the statistical results. Nevertheless, the small sample size of the included case-control studies, to a certain extent, limits the statistical power. Limited data were extracted for the CYP4AF2 rs C/T polymorphism subgroup with the diseases of ischemic stroke or myocardial infarction. Although no high degree of heterogeneity was observed in all meta-analyses of the CYP4AF2 rs polymorphism, high heterogeneity was observed in most of the overall meta-analyses of CYP4AF2 rs Apart from coronary heart disease and hypertension subgroup analyses, high heterogeneity still existed in other Asian, ischemic stroke and population-based subgroups. The complexity of disease feature might be the source of the large publication bias. In addition, unpublished data or

7 Zhang et al. BMC Cardiovascular Disorders (2018) 18:29 Page 7 of 10 Fig. 3 Subgroup analysis by disease type of the association between the CYP4AF2 rs polymorphism and the risk of cardiovascular and cerebrovascular diseases under the allele model articles in other languages may bias the selection of the studies analyzed. Given the complicated etiologies in different types of cardiovascular and cerebrovascular diseases [4, 39], additional relative factors, such as obesity, age, comorbidities, smoking, and drinking should be assessed. We spared no effort to retrieve the relative articles using the general terms and the specific forms of heart, cardiovascular and cerebrovascular diseases (e.g., myocardial infarction, coronary artery disease, or hypertension, etc.). However, limited data of the above relative factors were obtained. Only four case-control studies [8, 19, 25, 27] wereenrolled Table 3 The assessment of publication bias SNP Comparison Begg s test Egger s test z P value t P value rs C/T allele (T vs. C) homozygote (TT vs. CC) heterozygote (CT vs. CC) dominant (CT + TT vs. CC) recessive (TT vs. CC + CT) rs G/A allele (A vs. G) homozygote (AA vs. GG) heterozygote (GA vs. GG) dominant (GA + AA vs. GG) recessive (AA vs. GG + GA) SNP single nucleotide polymorphism

8 Zhang et al. BMC Cardiovascular Disorders (2018) 18:29 Page 8 of 10 Fig. 4 Begg s test and sensitivity analysis for the CYP4AF2 rs polymorphism under the allele model. a Funnel plot of Egger's test; b Sensitivity analysis to perform the male/female subgroup analysis for the association between CYP4AF2 rs and hypertension risk, while six studies [8, 19, 20, 23, 27, 32] were enrolled for CYP4F2 rs Adequate data on the genotype frequencies of both case and control studies are necessary to conduct SNP meta-analyses or subgroup analyses. Thus, only two SNPs (rs , rs ) were studied in the present metaanalysis based on the available data. We did not examine the role of other variants within the CYP4F2 gene, such as rs , rs , rs , and rs The G/G/G/T haplotype of rs rs rs rs has been associated with an increased risk of coronary artery disease, however the G/G/T/A haplotype was associated with a reduced risk of coronary heart disease [9]. The potential distinct effect of different haplotypes merits further study. In addition, the combined effect of CYP4F2 and other genes, such as CYP4A11 (Cytochrome P450 Family 4 Subfamily A Member 11), should be analyzed upon the publication of sufficient data. Conclusions Overall, the C/T genotype of the CYP4AF2 rs polymorphism might serve as a protective factor for male patients with hypertension in Asian populations, and CYP4AF2 rs may confer reduced genetic susceptibility to coronary heart disease.

9 Zhang et al. BMC Cardiovascular Disorders (2018) 18:29 Page 9 of 10 Additional files Additional file 1: Table S1-S7. Table S1. Details of the search strategy based on four databases. Table S2. Basic information of the eligible studies in the meta-analysis. Table S3. Data of NOS assessment system. Table S4. Genotype frequencies of the eligible studies in the metaanalysis. Table S5. Genotype frequencies of the male/female group in some eligible studies. Table S6. Subgroup analysis by gender for the association between CYP4AF2 rs and hypertension risk. Table S7. Subgroup analysis by gender for the association between CYP4AF2 rs and hypertension risk. (DOCX 63 kb) Additional file 2: Figure S1. Subgroup analysis by disease type of the association between the CYP4AF2 rs polymorphism and the risk of cardiovascular and cerebrovascular diseases under the allele (T vs. C) model.. (TIFF 887 kb) Additional file 3: Figure S2. Subgroup analysis by disease type of the association between the CYP4AF2 rs polymorphism and the risk of cardiovascular and cerebrovascular diseases under the dominant (CT + TT vs. CC) model. (TIFF 967 kb) Additional file 4: Figure S3. Subgroup analysis by gender of the association between the CYP4AF2 rs polymorphism and the risk of cardiovascular and cerebrovascular diseases under the allele (T vs. C) model. (TIFF 1958 kb) Additional file 5: Figure S4. Subgroup analysis by disease type of the association between the CYP4AF2 rs polymorphism and the risk of cardiovascular and cerebrovascular diseases under the homozygote (AA vs. GG) model. (TIFF 1760 kb) Additional file 6: Figure S5. Subgroup analysis by disease type of the association between the CYP4AF2 rs polymorphism and the risk of cardiovascular and cerebrovascular diseases under the heterozygote (GA vs. GG) model. (TIFF 1717 kb) Additional file 7: Figure S6. Subgroup analysis by disease type of the association between the CYP4AF2 rs polymorphism and the risk of cardiovascular and cerebrovascular diseases under the dominant (GA + AA vs. GG) model. (TIFF 1689 kb) Additional file 8: Figure S7. Subgroup analysis by disease type of the association between the CYP4AF2 rs polymorphism and the risk of cardiovascular and cerebrovascular diseases under the recessive (AA vs. GG + GA) model. (TIFF 1792 kb) Additional file 9: Figure S8. Subgroup analysis by gender of the association between the CYP4AF2 rs polymorphism and the risk of cardiovascular and cerebrovascular diseases under the allele (A vs. G) model. (TIFF 1045 kb) Abbreviations 20-HETE: 20-hydroxy eicosane arachidonic acid; AA: Arachidonic acid; CAD: Coronary artery disease; CIs: Confidence intervals; CYP4A11: Cytochrome P450 Family 4 Subfamily A Member 11; CYP4F2: Cytochrome P450 Family 4 Subfamily F Member 2; IS: Ischemic stroke; MI: Myocardial infarction; OR: Odds ratio; PRISMA: Preferred Reporting Items for Systematic Reviews and Meta- Analyses; SNPs: Single nucleotide polymorphisms Acknowledgments Not applicable. Funding Not applicable. Availability of data and materials All data generated or analyzed during the present study are included in this published article. Authors contributions TZ designed the study. TZ, KY and XL extracted, analyzed, and interpreted the data. TZ and KY drafted the manuscript. All authors read and approved the final version of the manuscript. Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare that they have no competing interests. Publisher s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Author details 1 First Department of Neurology, The First Hospital of Zibo, No.4 Emei Mountain Road, Boshan District, Zibo City, Shandong , People s Republic of China. 2 China Medical University Hospital of Boshan District, Zibo City, Shandong , People s Republic of China. Received: 6 December 2017 Accepted: 29 January 2018 References 1. Koberle B, Koch B, Fischer BM, Hartwig A. Single nucleotide polymorphisms in DNA repair genes and putative cancer risk. Arch Toxicol. 2016;90(10): Srinivasan S, Clements JA, Batra J. Single nucleotide polymorphisms in clinics: fantasy or reality for cancer? Crit Rev Clin Lab Sci. 2016;53(1): Chauhan G, Debette S. Genetic Risk factors for ischemic and hemorrhagic stroke. Curr Cardiol Rep. 2016;18(12): Della-Morte D, Pacifici F, Rundek T. 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